In the field of power integrated circuits much work has been done in the development of power transistors. Advancements were made enabling LDMOS power transistors (lateral double diffused MOS transistor) to exhibit low "on-resistance" (RDSon) and high breakdown capability concurrently through a reduced surface field (RESURF) technique (J. A. Appels and H. M. J. Vaes, "High Voltage Thin Layer Devices (RESURF Devices)", IEDM Tech. Digest, pp. 238-241, 1979).
In IC design, semiconductor die area is crucial. Generally, the larger the transistor area the lower "on" resistance (hereafter referred to as RDSon) the transistor exhibits. The design trade-off of transistor performance versus device cost becomes a crucial design constraint. This issue has driven research into new transistor structures that provide low RDSon while simultaneously minimizing transistor area. One improvement has been the development of a trench DMOS transistor (Ueda, Daisuke; Takagi, Hiromitsu; Kano, Gota; "An Ultra-Low On-Resistance Power MOSFET Fabricated by Using a Fully Self-Aligned Process", IEEE Transactions on Electron Device, Vol. ED-34, No.4, April 1987). The power transistor illustrated in the above mentioned publication has backside drain contact and is therefore unsuitable for integrating several independent devices on a single semiconductor substrate.
It is an object of this invention to provide a power transistor utilizing trench technology for applications requiring multiple, independent devices integrated onto a single semiconductor die. It is another object of this invention to provide a high voltage power transistor utilizing trench technology with electrical isolation between source and substrate. Other objects and advantages of the invention will become apparent to those of ordinary skill in the art having reference to the following specification and drawings.